The present invention relates to an apparatus for cleaning at least one continuous, long, linear object in a solvent medium. It also relates to the use of such an apparatus to clean at least one continuous, long, linear object.
In the present text, the term "continuous, long, linear object" is understood to mean an object of generally elongate shape, the longitudinal dimension of which is large compared with the dimensions of the object in a cross-section through a plane approximately perpendicular to the longitudinal dimension.
The continuous, long, linear objects in question are not rigid; they are substantially flexible and can be wound onto reels or into rolls.
Thus, the term "continuous, long, linear object" can denote a filiform object, an object in the form of ribbon, or an object consisting of unit elements joined together by suitable means to form a strip.
Examples of such continuous, long, linear objects that are intended to be cleaned by means of the present invention include filaments, threads and cables, for example made of metal, from which any trace of dirt must be removed, metal ribbons, magnetic tapes and photographic films, and electronic components soldered onto printed circuits (from which any trace of soldering flux must be removed) that are placed side-by-side and joined, for example by a support, to form a long, linear object having the appearance of a strip.
In the present text, the term "solvent medium" is understood to mean a liquid which contains at least one substance capable of bringing at least one other substance into solution. Thus, the solvent medium might be a fluorinated solvent or it can contain, for example, at least one organic and/or inorganic solvent or can alternatively be an alkaline or acid solution.
Apparatuses for cleaning objects of the previously mentioned types generally work by immersion of the object in the solvent medium. These apparatuses most frequently consist of an open vat having an inlet ramp and an outlet ramp in the region of its opening. The vat contains a liquid solvent medium that is chosen for its ability to dissolve the dirt present on the object. The solvent medium is generally heated, sometimes to a boil, and frequently subjected to the action of ultrasound up to the point of cavitation, which facilitates the extraction of dirt that is insoluble in the solvent medium. The liquid solvent medium is sometimes surmounted by a zone of hot saturated vapor of the solvent medium, and condensing means are provided in the top of the vat in order to prevent the vapor from escaping.
In an apparatus in which the solvent medium is surmounted by a zone of hot vapor, the long, linear object to be cleaned is moved through the vat in such a way as to pass successively through the vapor zone, the solvent medium and the vapor zone again. When the object passes through the vapor zone for the first time, it is preheated as a result of the vapor condensing on its surface. This action inhibits thermal shock to the object which is immersed in the hot solvent medium. Further, the object is pre-cleaned by the trickles of condensate. When the object passes through the vapor zone for the second time, it is rinsed by the trickles of solvent that has condensed on it.
In general, the object is moved through the vat by exerting a pulling force on it using drawing means, such as a means for winding the object into a roll. Whether or not the liquid solvent medium is surmounted by a vapor zone, the object moves through the vat along a trajectory and at a speed which are such that the residence time of the object in the solvent medium is sufficient to ensure that the object is properly cleaned.
In some apparatuses, the object moves along a free trajectory between the inlet ramp and the outlet ramp and, in the case where the object is moving too fast, there is nothing to prevent the object from following too short a path through the solvent medium or even from coming out of the medium. To overcome this disadvantage, some apparatuses are provided with rollers that freely rotate around their axes, and the long, linear object then moves through the solvent medium along a broken-line trajectory.
An apparatus of this type prevents any inopportune emergence of the long, linear object from the solvent medium, but the rollers considerably increase the risks of damaging the long, linear object. In the case of cleaning electronic circuits, this damage can even extend to pulling the components off.
Furthermore, as the solvent medium is frequently caustic, especially when it is being subjected to cavitation, there are considerable problems of corrosion of the rollers and their supports.